Recently, with remarkable development of the radio connection of a mobile terminal, interests in mutual connection and handover among different radio networks having different radio connection technologies are increasing.
In particular, in mutual connection between a mobile communication network and a wireless local area network (WLAN), the WLAN having narrow coverage is provided to overlap the densely populated area of a mobile communication network having wide coverage so that a user of the mobile terminal can use IP based multimedia services at a low price and that a mobile terminal network enterpriser can reduce network construction cost and communication load in the densely populated area and can disperse users. Therefore, interest in the mutual connection between the mobile communication network and the WLAN is increasing.
In such an environment, a mobile communication system having a completely different network connection method and a mobile terminal to which all kinds of WLAN systems can be connected are required. Furthermore, connection procedures, subscriber authentication technologies, charging technologies, mobility technologies, and quality of service (QoS) technologies that are required by the networks are to be accepted.
In addition, in the above-described mutual connection between the mobile communication network and the WLAN, there are many difficulties in connection setup procedures so that it is difficult to apply the connection procedures of the conventional WLAN to the mobile communication network and, reversely, to apply the connection procedures of the mobile communication network to the WLAN. Therefore, the handover of the mobile terminal among different networks is limited.